Control apparatus of engine

ABSTRACT

A control apparatus of an engine including intake and exhaust valves and a variable valve timing mechanism for varying open and close timings is provided. The apparatus includes a processor configured to execute an increasing amount controlling module for performing a fuel amount increase control in which a fuel injection amount is increased to decrease an exhaust gas temperature, and a valve controlling module for controlling, via the variable valve timing mechanism, an overlapping period in which the intake and exhaust valves are both opened on intake stroke. When the increasing amount controlling module performs the increase control, based on an increase of a temperature of the exhaust gas in the increase control, the valve controlling module determines whether a protection for an exhaust system component is required, and if the protection is determined to be required, the valve controlling module shortens the overlapping period.

BACKGROUND

An art disclosed here relates to a control apparatus of an engine.

For control apparatuses of engines, an art of controlling an overlappingperiod in which an intake valve and an exhaust valve are both opened onintake stroke is known.

For example, JP2012-163047A discloses a control apparatus of an engine,which shortens the overlapping period based on an estimation result of acatalyst temperature, so that the catalyst temperature does notexcessively increase due to combustion of remaining gas scavenged from acylinder.

In general, to cool exhaust gas, an amount of fuel injected into thecylinder may be increased. In this case, since unburned fuel vaporizesinside the cylinder, latent heat of the vaporization cools the inside ofthe cylinder, and a temperature of the exhaust gas discharged from thecylinder to an exhaust system decreases.

Here, if the overlapping period is set, fresh air blows through anintake system to the exhaust system, the unburned fuel may react withthe blown-through fresh air in the exhaust system and cause a so-calledafterburn. By this afterburn, various components of the exhaust systemmay excessively increase in temperature.

SUMMARY

The present invention is made in view of the above problems, and aims toprotect various components of an exhaust system.

According to one aspect of the present invention, a control apparatus ofan engine including an intake valve, an exhaust valve, and a variablevalve timing mechanism for varying open and close timings of at leastone of the intake and exhaust valves is provided. The apparatuscomprises a processor configured to execute an increasing amountcontrolling module for performing a fuel amount increase control inwhich an injection amount of fuel is increased so as to decrease atemperature of exhaust gas, and a valve controlling module forcontrolling, via the variable valve timing mechanism, an overlappingperiod in which the intake and exhaust valves are both opened on intakestroke of the engine. When the increasing amount controlling moduleperforms the fuel amount increase control, based on a temperatureincrease of the exhaust gas estimated to occur due to the fuel amountincrease control, the valve controlling module determines whether aprotection for a component of an exhaust system of the engine isrequired, and if the protection for the component of the exhaust systemis determined to be required, the valve controlling module shortens theoverlapping period.

With the above configuration, based on the temperature increase of theexhaust gas in the fuel amount increase control, whether the protectionfor the component of the exhaust system is required is determined, andif the protection for the component of the exhaust system is determinedto be required, the overlapping period is shortened. Since the exhaustgas temperature increases when afterburn occurs, by performing thedetermination based on the temperature increase of the exhaust gas, thetiming at which the protection for the component of the exhaust systemis required can be determined more suitably. Further, since a flow rateof fresh air blown through to the exhaust system is decreasedcorresponding to the shortened amount of the overlapping period, theafterburn is suppressed according to the decrease amount. Therefore, thetemperature increase of the component of the exhaust system can besuppressed to protect the component.

Further, if the protection for the component of the exhaust system isdetermined to be required, the valve controlling module may shorten theoverlapping period before the increasing amount controlling modulestarts increasing the injection amount.

With the above configuration, the overlapping period is shortened beforethe fuel amount increase starts. Thus, by the time the increased amountof fuel is supplied to the exhaust system, the blow-through flow rate ofthe fresh air has decreased already. Therefore, the afterburn can besuppressed more surely, which advantageously results in protecting thecomponent of the exhaust system.

Further, the valve controlling module may determine whether theprotection for the component of the exhaust system is required, based ona flow rate of fresh air blowing to the exhaust system in theoverlapping period, and the injection amount.

The exhaust gas temperature may increase due to afterburn which occursby a reaction of the fresh air blown through to the exhaust system withunburned fuel in the exhaust system. The amount of the unburned fuelchanges according to the fuel injection amount. Thus, with the aboveconfiguration, by performing the determination in consideration of theblow-through flow rate of the fresh air and the fuel injection amount,the temperature increase of the exhaust gas caused by the afterburn canbe accurately estimated. Thus, whether the protection for the componentof the exhaust system is required can accurately be determined.

Further, the valve controlling module may determine that the protectionfor the component of the exhaust system is required, in the case wherethe fuel amount increase control is performed and the exhaust gastemperature is above a given protection determination temperature, or inthe case where the fuel amount increase control is performed and atemperature of the component of the exhaust system is above a givendetermination component temperature.

Generally, the exhaust gas temperature and the component temperature areconsidered to increase according to the temperature increase of theexhaust gas in the fuel amount increase control. Thus, with the aboveconfiguration, by performing the determination based on the temperatureof the exhaust gas or the component, the timing at which the protectionfor the component of the exhaust system is required can be determinedmore suitably.

Further, the valve controlling module may set a shortening amount of theoverlapping period based on the temperature increase of the exhaust gas.

With the above configuration, by taking into consideration thetemperature increase of the exhaust gas in setting the shortening amountof the overlapping period, the temperature increase of the component ofthe exhaust system can be suppressed more surely. For example, byincreasing the shortening amount as the temperature increase of theexhaust gas becomes larger, the blow-through flow rate can be decreasedmore as the temperature increase becomes larger. Thus, the afterburn canbe suppressed more sufficiently, and as a result, the temperatureincrease of the component of the exhaust system can be suppressed moresurely.

Further, the valve controlling module may change the open and closetimings of the exhaust valve when shortening the overlapping period.

With the above configuration, compared with a case of changing the openand close timings of the intake valve, an influence on an amount ofintake air supplied into a cylinder of the engine can be reduced and, asa result, by providing the overlapping period, an influence on an outputtorque of the engine is advantageously reduced.

Further, the component of the exhaust system may at least include acatalyst for purifying the exhaust gas.

With the above configuration, at least the catalyst can be protectedfrom the heat of the exhaust gas.

According to one aspect of the present invention, a control apparatus ofan engine including an intake valve, an exhaust valve, and a variablevalve timing mechanism for varying open and close timings of at leastone of the intake and exhaust valves is provided. The apparatuscomprises a processor configured to execute an increasing amountcontrolling module for setting an injection amount of fuel in responseto a request from a driver and performing, based on a temperature ofexhaust gas, a fuel amount increase control in which the injectionamount of the fuel is increased so as to decrease the temperature of theexhaust gas, and a valve controlling module for controlling, via thevariable valve timing mechanism, an overlapping period in which theintake and exhaust valves are both opened on intake stroke of theengine. When the increasing amount controlling module performs the fuelamount increase control, based on a temperature increase of the exhaustgas estimated to occur due to the fuel amount increase control, thevalve controlling module determines whether a protection for a componentof an exhaust system of the engine is required, and if the protectionfor the component of the exhaust system is determined to be required,the valve controlling module shortens the overlapping period.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic configuration view of an engine.

FIG. 2 is a function block diagram of an ECU.

FIG. 3 is a flowchart of base setting.

FIG. 4 is a view illustrating an operation model used for estimating anexhaust gas temperature.

FIG. 5 is an image chart of an exhaust gas temperature map.

FIG. 6 is an image chart of a blow-through cooling map.

FIG. 7 is an image chart of a manifold section temperature increase map.

FIG. 8 is an image chart of a first afterburn map.

FIG. 9 is an image chart of a first coefficient map.

FIG. 10 is an image chart of an upstream-side vehicle speed heat releasemap.

FIG. 11 is an image chart of a downstream-side vehicle speed heatrelease map.

FIG. 12 is an image chart of a second coefficient map.

FIG. 13 is an image chart of a third coefficient map.

FIG. 14 is an image chart of a work loss map.

FIG. 15 is an image chart of a fourth coefficient map.

FIG. 16 is an image chart of a reaction heat map.

FIG. 17 is an image chart of a fifth coefficient map.

FIG. 18 is an image chart of a second afterburn map.

FIG. 19 is a flowchart illustrating processing of a fuel amount increasecontrol.

DETAILED DESCRIPTION OF EMBODIMENTS

Hereinafter, illustrative embodiments are described with reference tothe appended drawings.

Engine Configuration

FIG. 1 is a schematic configuration view of an engine to which a controlapparatus according to this embodiment is applied.

As illustrated in FIG. 1, the engine 100 (e.g., gasoline engine) ismounted on a vehicle and mainly has an intake passage (intake system) 10through which intake air (air) externally introduced passes, an enginebody 20 to which the intake passage 10 is coupled, an exhaust passage(exhaust system) 30 coupled to the engine body 20, and an ECU(Electronic Control Unit) 50 for controlling the entire engine 100.

In the intake passage 10, an air cleaner 2 for purifying the externallyintroduced intake air, a compressor 4 a provided to a turbocharger 4 andfor pressurizing the intake air passing therethrough, an intercooler 9for cooling the intake air passing therethrough, a throttle valve 11 foradjusting a flow rate of the intake air passing therethrough, and anintake manifold 13 having a surge tank 13 a for temporarily storing theintake air supplied to the engine body 20 are arranged in this orderfrom an upstream side. The intake manifold 13 is connected with intakeports 14 of the engine body 20.

Further in the intake passage 10, an air bypass passage 6 forrecirculating a part of the intake air turbocharged by the compressor 4a back to an upstream side of the compressor 4 a is provided. One end ofthe air bypass passage 6 is connected with the intake passage 10 at aposition downstream of the compressor 4 a and upstream of the throttlevalve 11, and the other end of the air bypass passage 6 is connectedwith the intake passage 10 at a position upstream of the compressor 4 a.Moreover, an air bypass valve 7 for controlling a flow rate of theintake air passing through the air bypass passage 6 is provided to theair bypass passage 6.

The engine body 20 mainly has intake valves 22 for opening and closingthe intake ports 14, respectively, fuel injectors 23 for injecting thefuel into cylinders 21, respectively, ignition plugs 24 for ignitingmixture gas containing the intake air and the fuel supplied into thecylinders 21, respectively, pistons 27 for being reciprocated bycombustion of the mixture gas inside the cylinders 21, respectively, acrankshaft 28 for rotating in relation to the reciprocations of thepistons 27, and exhaust valves 29 for opening and closing exhaust ports31.

An intake camshaft and an exhaust camshaft (not illustrated) are coupledto the crankshaft 28 to be driven thereby. The intake camshaft rotatesin conjunction with the crankshaft 28 to drive the intake valves 22.Thus, each intake valve 22 reciprocates to open and close the intakeport 14 at given timings. Similarly, the exhaust camshaft rotates inconjunction with the crankshaft 28 to drive the exhaust valves 29. Thus,each exhaust valve 29 reciprocates to open and close the exhaust port 31at given timings.

The engine body 20 includes a variable valve timing mechanism (intakeVVT) 25 for advancing or retarding a phase of the intake camshaft, and avariable valve timing mechanism (exhaust VVT) 26 for advancing orretarding a phase of the exhaust camshaft.

The intake VVT 25 varies each of the open and close timings of theintake valve 22 between a most-advanced timing and a most-retardedtiming by advancing or retarding the phase of the intake camshaft. Inthis embodiment, the intake VVT 25 includes an electromagnetic valve.Similarly, the exhaust VVT 26 varies each of the open and close timingsof the exhaust valve 29 by advancing or retarding the phase of theexhaust camshaft. In this embodiment, the exhaust VVT 26 includes ahydraulic solenoid valve.

In the exhaust passage 30, a turbine 4 b provided to the turbocharger 4and for rotating by letting exhaust gas pass therethrough so as torotate the compressor 4 a, and exhaust emission control catalysts 37 and38 having an exhaust gas purifying function are arranged in this orderfrom an upstream side. The exhaust emission control catalysts 37 and 38are, for example, an NOx catalyst, a three-way catalyst, and/or anoxidation catalyst.

An upstream end part of an exhaust pipe forming the exhaust passage 30has branched pipes 30 a coupled to the respective exhaust ports 31, anda manifold section 30 b where the branched pipes 30 a are collectedtogether. One or some of the branched pipes 30 a are formed by anexhaust manifold.

Further, the exhaust passage 30 is connected with an EGR (Exhaust GasRecirculation) passage 32 for recirculating the exhaust gas back to theintake passage 10. One end of the EGR passage 32 is connected with theexhaust passage 30 at a position upstream of the turbine 4 b, and theother end of the EGR passage 32 is connected with the intake passage 10at a position downstream of the throttle valve 11. Additionally, in theEGR passage 32, an EGR cooler 33 for cooling the exhaust gas to berecirculated, and an EGR valve 34 for controlling a flow rate of theexhaust gas passing through the EGR passage 32, are provided.

Further in the exhaust passage 30, a turbine bypass passage 35 forcausing the exhaust gas to bypass the turbine 4 b of the turbocharger 4is formed. A wastegate valve (hereinafter, referred to as the “WGvalve”) 36 for controlling a flow rate of the exhaust gas passingthrough the turbine bypass passage 35 is provided to the turbine bypasspassage 35.

Moreover, various sensors are provided in the engine 100 illustrated inFIG. 1. Specifically, in the intake system of the engine 100, an airflowsensor 61 for detecting an intake air flow rate and a first temperaturesensor 62 for detecting an intake air temperature are provided in theintake passage 10 at positions downstream of the air cleaner 2(specifically, positions between the air cleaner 2 and the compressor 4a), a first pressure sensor 63 for detecting turbocharging pressure isprovided in the intake passage 10 at a position between the compressor 4a and the throttle valve 11, and a second pressure sensor 64 fordetecting an intake-manifold pressure which is a pressure inside thesurge tank 13 a is provided in the intake passage 10 at a positiondownstream of the throttle valve 11 (specifically, inside the surge tank13 a). A temperature sensor for detecting an intake-manifold temperaturewhich is a temperature inside the surge tank 13 a is built in the secondpressure sensor 64.

Further in the engine body 20, a crank angle sensor 69 for detecting acrank angle of the crankshaft 28, an intake cam angle sensor 70 fordetecting a cam angle of the intake camshaft, and an exhaust cam anglesensor 71 for detecting a cam angle of the exhaust camshaft areprovided.

Moreover, in the exhaust system of the engine 100, an EGR opening sensor65 for detecting an EGR opening which is an opening of the EGR valve 34,and a WG opening sensor 66 for detecting a WG opening which is anopening of the WG valve 36 are provided. An O₂ sensor 67 for detectingan oxygen concentration within the exhaust gas, and an exhaust gastemperature sensor 68 for detecting an exhaust gas temperature areprovided in the exhaust passage 30 at positions downstream of theturbine 4 b (specifically, positions between the turbine 4 b and theexhaust emission control catalyst 37).

The airflow sensor 61 supplies to the ECU 50 a detection signal S61corresponding to the detected intake air flow rate. The firsttemperature sensor 62 supplies to the ECU 50 a detection signal S62corresponding to the detected intake air temperature, and the firstpressure sensor 63 supplies to the ECU 50 a detection signal S63corresponding to the detected turbocharging pressure. The secondpressure sensor 64 supplies to the ECU 50 a detection signal S64corresponding to the detected intake-manifold pressure and temperature.The EGR opening sensor 65 supplies to the ECU 50 a detection signal S65corresponding to the detected EGR opening. The WG opening sensor 66supplies to the ECU 50 a detection signal S66 corresponding to thedetected WG opening. The O₂ sensor 67 supplies to the ECU 50 a detectionsignal S67 corresponding to the detected oxygen concentration. Theexhaust gas temperature sensor 68 supplies to the ECU 50 a detectionsignal S68 corresponding to the detected exhaust gas temperature. Thecrank angle sensor 69 supplies to the ECU 50 a detection signal S69corresponding to the detected crank angle. The intake and exhaust camangle sensors 70 and 71 supply to the ECU 50 detection signals S70 andS71 corresponding to the detected cam angles, respectively. Further, theengine 100 is provided with an atmospheric pressure sensor 60 fordetecting an atmospheric pressure, and the atmospheric pressure sensor60 supplies to the ECU 50 a detection signal S60 corresponding to thedetected atmospheric pressure.

The ECU 50 includes a computer comprised of a processor 55 (see FIG. 2)and internal memories, such as ROMs and RAMs for storing variousprograms which are executed by the processor 55, and various data. Thevarious programs include a basic control program (e.g., operating system(OS)) and an application program which is activated by the OS andrealizes a particular function. The ECU 50 performs various controls andoperations based on the detection signals transmitted from the varioussensors described above.

For example, in response to a request from a driver of the vehicle, theECU 50 sets an opening of the throttle valve 11, a fuel injection amountof each fuel injector 23, etc., estimates an exhaust gas temperature,and adjusts the fuel injection amount and the open and close timings ofthe intake and exhaust valves 22 and 29 according to the exhaust gastemperature.

FIG. 2 is a function block diagram of the ECU 50. Specifically, the ECU50 includes a base setting module 51 for performing a torque basecontrol in which base values in controls of the throttle valve 11 etc.are set, a temperature estimating module 52 for estimating the exhaustgas temperature, an increasing amount controlling module 53 forperforming a fuel amount increase control in which the injection amountis increased to decrease the exhaust gas temperature, a valvecontrolling module 54 for controlling an overlapping period of theintake and exhaust valves 22 and 29, and the processor 55 for executingthe various modules of the ECU 50.

The base setting module 51 obtains a required torque (hereinafter,referred to as the “target torque”) based on an operating state of theengine 100, and sets base values of the opening of the throttle valve11, the opening of the WG valve 36, an ignition timing of each ignitionplug 24, the open and close timings of each intake valve 22, the openand close timings of each exhaust valve 29, and the injection amount ofthe fuel injector 23, according to the target torque, etc. Each of thebase values is changed variously according to the target torque.

The temperature estimating module 52 estimates the exhaust gastemperature by calculating a gain and loss of heat of the exhaust gasfrom the cylinder 21 to the exhaust emission control catalyst 37. Thetemperature estimating module 52 estimates the exhaust gas temperaturein various parts of the exhaust passage 30 (e.g., upstream of theturbine 4 b, the O₂ sensor 67, and the exhaust emission control catalyst37).

The increasing amount controlling module 53 increases the injectionamount set by the base setting module 51, according to the exhaust gastemperatures estimated by the temperature estimating module 52. In otherwords, the increasing amount controlling module 53 controls the fuelinjector 23 to inject a sufficient amount of fuel in achieving thetarget torque. By increasing the fuel amount as above, a temperatureinside the cylinder 21 is decreased by latent heat of vaporization ofthe fuel, and as a result, the exhaust gas temperatures are decreased.

The valve controlling module 54 basically controls the intake andexhaust VVTs 25 and 26 to realize the open and close timings of theintake and exhaust valves 22 and 29 set by the base setting module 51.Depending on the operating state of the engine 100, the open and closetimings of the intake and exhaust valves 22 and 29 may be adjusted sothat the open timing of the intake valve 22 overlaps with the opentiming of the exhaust valve 29 on intake stroke. In such a case, thevalve controlling module 54 performs a valve overlap control in whichthe intake and exhaust valves 22 and 29 are both opened on the intakestroke. By performing the valve overlap control, fresh air sucked intothe cylinder 21 via the intake port 14 is discharged from the exhaustport 31 as-is. The valve overlap control is performed to, for example,stimulate scavenging of the cylinder 21, decrease the temperature of thecylinder 21, or increase a turbine flow rate.

Additionally, the valve controlling module 54 adjusts the overlappingperiod which is a period in which the intake and exhaust valves 22 and29 are both opened. Specifically, when the exhaust gas temperaturesestimated by the temperature estimating module 52 are high, the valvecontrolling module 54 adjusts the overlapping period to reduce anoverlapping amount between the open timings of the intake and exhaustvalves 22 and 29.

Torque Base Control

First, a torque base control is described in detail with reference to aflowchart of FIG. 3. FIG. 3 is a flowchart of base setting.

First at S101, the base setting module 51 acquires the operating stateof the engine 100. Specifically, a speed of the engine body 20(hereinafter, referred to as the “engine speed”), a vehicle speed, anaccelerator opening, a transmission ratio, etc. are read based ondetection results of the various sensors. For example, the engine speedis acquired based on the detection result of the crank angle sensor 69.

Next, the base setting module 51 obtains a target acceleration accordingto the acquired operating state (S102). Further, the base setting module51 obtains the target torque required to achieve the target acceleration(S103).

Moreover, at S104, the base setting module 51 obtains a target value ofa charge efficiency of the fresh air required to achieve the targettorque (hereinafter, referred to as the “target charge efficiency”).Specifically, the target charge efficiency is obtained based on thetarget torque, the engine speed, and a target value of an indicated meaneffective pressure (hereinafter, referred to as the “target indicatedmean effective pressure”). The target indicated mean effective pressureis obtained based on the target torque, and also a mechanical resistanceand a pumping loss which correspond to a torque loss.

The base setting module 51 sets the base values of the open and closetimings of the intake and exhaust valves 22 and 29 based on the targetcharge efficiency set as above. The base values of the open and closetimings of the intake valve 22 are obtained based on an intake VVT mapstored in advance in the internal memory of the ECU 50 and in which theengine speed and the target charge efficiency, and the open and closetimings of the intake valve 22 are defined in association with eachother. Similarly, the base values of the open and close timings of theexhaust valve 29 are obtained based on an exhaust VVT map stored inadvance in the internal memory of the ECU 50 and in which the enginespeed and the target charge efficiency, and the open and close timingsof the exhaust valve 29 are defined in association with each other.Basically, the base values of the open and close timings of the intakevalve 22 are set so that the intake valve 22 opens on the intake strokeand closes on compression stroke after the piston 27 passes a bottomdead center. In other words, the intake valve 22 is designed to performso-called late closing. Further, depending on the engine speed and thetarget charge efficiency, the base values of the open and close timingsof the exhaust valve 29 are set so that the overlapping period isprovided on the intake stroke.

After S104, S105 to S108 and S109 to S112 are performed in parallel toeach other.

At S105, the base setting module 51 obtains a target value of the intakeair amount inside the intake manifold 13 (hereinafter, referred to asthe “target intake-manifold air amount”) required to achieve the targetcharge efficiency. The target intake-manifold air amount is obtainedbased on the intake-manifold temperature detected by the second pressuresensor 64, a target value of the intake-manifold pressure (hereinafter,referred to as the “target intake-manifold pressure”), and the open andclose timings of the intake valve 22. The target intake-manifoldpressure is obtained based on an intake characteristics map stored inadvance in the internal memory of the ECU 50 and in which the targetintake-manifold air amount and the intake-manifold temperature and thetarget intake-manifold pressure are defined in association with eachother.

At S106, the base setting module 51 obtains a target value of the flowrate of the intake air passing through the throttle valve 11(hereinafter, referred to as the “target throttle flow rate”) requiredto achieve the target intake-manifold air amount. The target throttleflow rate is obtained based on the target charge efficiency obtained atS104, the target intake-manifold air amount obtained at S105, and anestimated value of a current intake-manifold air amount (hereinafter,referred to as the “actual intake-manifold air amount”). The actualintake-manifold air amount is estimated based on the intake-manifoldpressure and temperature detected by the second pressure sensor 64. Notethat the actual intake-manifold air amount may be estimated bycalculating a gain and loss between an amount of air flowing into theintake manifold 13 and an amount of air flowing into the cylinder 21from the intake manifold 13.

At S107, the base setting module 51 obtains a target value of theopening of the throttle valve 11 (hereinafter, referred to as the“target throttle opening”) required to achieve the target throttle flowrate. The target throttle opening is obtained based on the targetthrottle flow rate, the intake pressure upstream of the throttle valve11 (turbocharging pressure), which is detected by the first pressuresensor 63, and the intake pressure downstream of the throttle valve 11,which is detected by the second pressure sensor 64.

At S108, the base setting module 51 also obtains the base values for thefuel injector 23 and the ignition plug 24, based on suitable maps storedin advance in the internal memory of the ECU 50. For example, the basesetting module 51 sets the injection amount of the fuel injector 23based on the target charge efficiency, and sets the ignition timing ofthe ignition plug 24 to achieve the target torque. Then, the basesetting module 51 outputs control signals corresponding to controlvalues (base values) to the intake valve 22, the fuel injector 23, theignition plug 24, and the intake and exhaust VVTs 25 and 26.

On the other hand, at S109, the base setting module 51 obtains a targetvalue of the turbocharging pressure (hereinafter, referred to as the“target turbocharging pressure”) required to achieve the target chargeefficiency. The target turbocharging pressure is obtained based on aturbocharging pressure map stored in advance in the internal memory ofthe ECU 50 and in which the engine speed, the target charge efficiency,and the open and close timings of the intake valve 22, and the targetturbocharging pressure are defined in association with each other.

At S110, the base setting module 51 obtains a target value of the flowrate through the turbine 4 b (hereinafter, referred to as the “targetturbine flow rate”) based on the target turbocharging pressure.Specifically, the target turbine flow rate is obtained based on a targetvalue of a compressor drive force (target compressor drive force), theengine speed, etc. The target compressor drive force is obtained basedon the target turbocharging pressure.

At S111, the base setting module 51 sets a target value of the openingof the WG valve 36 (hereinafter, referred to as the “target WG opening”)required to achieve the target turbine flow rate. The target WG openingis obtained based on the target turbine flow rate and a total flow rateof the exhaust gas.

Then, at S112, the base setting module 51 outputs a control signal tothe WG valve 36 to cause it to open at the target WG opening.

Note that the order of these steps is an example and may suitably bechanged, or some of these steps may be performed in parallel. Forexample, S105 to S108 and S109 to S112 may be performed one by one,instead of performing them in parallel.

As above, the base setting module 51 sets the respective base values ofthe opening of the throttle valve 11, the injection amount of the fuelinjector 23, the ignition timing of the ignition plug 24, the open andclose timings of the intake and exhaust valves 22 and 29, and theopening of the WG valve 36.

Temperature Estimation

Next, a temperature estimation of the temperature estimating module 52is described in detail with reference to FIG. 4. FIG. 4 is a viewillustrating an operation model used for estimating the exhaust gastemperature.

The temperature estimating module 52 estimates the gain and loss in heatrelease and reception in a period from the exhaust gas being dischargedfrom the cylinder until it reaches the exhaust emission control catalyst37, and estimates the exhaust gas temperatures at the plurality oflocations in the exhaust system. Specifically, the temperatureestimating module 52 estimates (A) a first exhaust gas temperature Ta atan exit of each exhaust port 31, (B) a second exhaust gas temperature Tbat a position immediate upstream of the turbine 4 b, (C) a third exhaustgas temperature Tc at the O₂ sensor 67, and (D) a fourth exhaust gastemperature Td at the exhaust emission control catalyst 37. For the gainand loss of the heat, the temperature estimating module 52 takes intoconsideration (i) heat release to the exhaust port 31 cooled by thefresh air blowing therethrough, (ii) heat reception from the manifoldsection 30 b of the exhaust pipe, (iii) heat reception caused byafterburn at a position of the exhaust pipe upstream of the turbine 4 b,(iv) heat release to a part of the exhaust pipe upstream of the turbine4 b (the upstream of the turbine 4 b includes the exhaust manifold and aturbine housing), (v) heat release to a part of the exhaust pipedownstream of the turbine 4 b and upstream of the exhaust emissioncontrol catalyst 37, (vi) a heat loss caused by the work of the turbine,(vii) heat reception from reaction heat of the exhaust emission controlcatalyst 37, and (viii) heat reception caused by afterburn at theexhaust emission control catalyst 37.

Specifically, the temperature estimating module 52 first estimates atemperature of the exhaust gas combusted in and discharged from thecylinder 21 (hereinafter, referred to as the “discharging temperature”)T0. The discharging temperature T0 is calculated based on the enginespeed, the charge efficiency, the ignition timing (retarded amount), andan air-fuel ratio. The internal memory of the ECU 50 stores in advancean exhaust gas temperature map in which the discharging temperature T0based on the engine speed, the charge efficiency, the ignition timing,and the air-fuel ratio is defined. FIG. 5 is an image chart of theexhaust gas temperature map in which the discharging temperature T0becomes higher as the engine speed increases, the charge efficiencyincreases, the ignition timing is retarded, and the air-fuel ratioincreases. The temperature estimating module 52 obtains the dischargingtemperature T0 by comparing the engine speed, the charge efficiency, theignition timing, and the air-fuel ratio with the exhaust gas temperaturemap. Note that various maps used for the temperature estimation by thetemperature estimating module 52, including the exhaust gas temperaturemap, are unique to every engine 100 and obtained in advance by actualmeasurements etc. Therefore, the exhaust gas temperature map of FIG. 5and various maps described later are merely examples, and they mayindicate different characteristics depending on the engine.

The temperature estimating module 52 obtains an amount of decrease ofthe exhaust gas temperature due to (i) the heat release to the exhaustport 31 cooled by the fresh air blowing therethrough (hereinafter, thedecrease amount is referred to as the “first temperature decrease amountΔTe1”). Because of the fresh air blowing through the exhaust port 31,the exhaust port 31 (in other words, a cylinder head of the engine) iscooled. Thus, the exhaust gas passing through the exhaust port 31 isalso cooled, and the exhaust gas temperature decreases. The firsttemperature decrease amount ΔTe1 of the exhaust gas resulting from theblow-through of the fresh air increases as a flow rate of the fresh airblowing through increases (i.e., the exhaust gas is cooled more).

First, the temperature estimating module 52 calculates the blow-throughflow rate. Specifically, the temperature estimating module 52 calculatesa base value of a blow-through rate based on the intake pressure (theintake-manifold pressure detected by the second pressure sensor 64), andthe overlapping amount of the intake and exhaust valves 22 and 29 (i.e.,overlapping period). The overlapping amount is obtained based on theopen and close timings of the intake and exhaust valves 22 and 29. Theinternal memory of the ECU 50 stores in advance a blow-through rate mapin which the base value of the blow-through rate based on the intakepressure and the overlapping amount is defined. The temperatureestimating module 52 obtains the base value of the blow-through rate bycomparing the intake pressure and the overlapping amount with theblow-through rate map. Further, the internal memory of the ECU 50 storesin advance a correction map in which a correction term of theblow-through rate based on the engine speed is defined. The temperatureestimating module 52 obtains the correction term of the blow-throughrate by comparing the engine speed with the correction map. Then, thetemperature estimating module 52 obtains an applied value of theblow-through rate by multiplying the base value of the blow-through rateby the correction term thereof. Additionally, the temperature estimatingmodule 52 calculates the blow-through flow rate by multiplying an intakeair flow rate by the blow-through rate. The intake air flow rate may bethe intake air flow rate detected by the airflow sensor 61. The internalmemory of the ECU 50 stores in advance a blow-through cooling map inwhich the first temperature decrease amount ΔTe1 based on theblow-through flow rate is defined. FIG. 6 is an image chart of theblow-through cooling map in which the first temperature decrease amountΔTe1 increases as the blow-through flow rate increases. The temperatureestimating module 52 obtains an applied value of the first temperaturedecrease amount ΔTe1 by comparing the blow-through flow rate with theblow-through cooling map.

The temperature estimating module 52 obtains the first exhaust gastemperature Ta at the exit of the exhaust port 31 by subtracting thefirst temperature decrease amount ΔTe1 from the discharging temperatureT0.

The temperature estimating module 52 obtains an increase amount of theexhaust gas temperature due to (ii) the heat reception from the manifoldsection 30 b of the exhaust pipe (hereinafter, this increase amount isreferred to as the “first temperature increase amount ΔTi1”). In otherwords, the exhaust gas is intermittently discharged at a hightemperature from the exhaust port 31 of each cylinder in a combustionorder of the cylinders 21. The exhaust gas intermittently dischargedfrom each cylinder 21 passes through the corresponding branched pipe 30a and eventually reaches the manifold section 30 b. Therefore, since theexhaust gas from the plurality of cylinders sequentially flows into themanifold section 30 b, a temperature of the manifold section 30 bincreases compared with the branched pipes 30 a. Since the temperatureof the manifold section 30 b increases as above, the exhaust gas isincreased in temperature by passing through the manifold section 30 b.The internal memory of the ECU 50 stores in advance a manifold sectiontemperature increase map in which the first temperature increase amountΔTi1 based on the first exhaust gas temperature Ta is defined. FIG. 7 isan image chart of the manifold section temperature increase map in whichthe first temperature increase amount ΔTi1 increases as the firstexhaust gas temperature Ta increases (i.e., the exhaust gas is heatedmore). The temperature estimating module 52 obtains the firsttemperature increase amount ΔTi1 by comparing the first exhaust gastemperature Ta with the manifold section temperature increase map.

The temperature estimating module 52 obtains an increase amount of theexhaust gas temperature due to (iii) the heat reception caused by theafterburn in the upstream part of the exhaust pipe (hereinafter, thisincrease amount is referred to as the “second temperature increaseamount ΔTi2”). When the blow-through of the fresh air occurs, the freshair flows into the exhaust pipe. Therefore, if the exhaust gas containsthe unburned fuel, the fresh air reacts with the unburned fuel in theexhaust pipe and a so-called afterburn occurs. Particularly since thetemperature of the exhaust gas increases in the manifold section 30 b ofthe exhaust pipe, the afterburn easily occurs. The internal memory ofthe ECU 50 stores in advance a first afterburn map in which a base valueof the second temperature increase amount ΔTi2 based on the blow-throughflow rate is defined, and a first coefficient map in which a coefficientbased on the air-fuel ratio (hereinafter, referred to as the “firstcoefficient α1”) is defined. FIG. 8 is an image chart of the firstafterburn map in which the base value of the second temperature increaseamount ΔTi2 increases as the blow-through flow rate increases (i.e., theexhaust gas is heated more). FIG. 9 is an image chart of the firstcoefficient map in which the first coefficient α1 decreases (i.e., theexhaust gas is heated less) as the air-fuel ratio shifts to be richer(the air-fuel ratio decreases) from a stoichiometric ratio (14.7:1).This is because an influence of the cooling effect caused by the latentheat of the vaporization increases as the air-fuel ratio becomes richer.The temperature estimating module 52 obtains the base value of thesecond temperature increase amount ΔTi2 by comparing the blow-throughflow rate with the first afterburn map, and the first coefficient α1 bycomparing the air-fuel ratio with the first coefficient map. Thetemperature estimating module 52 obtains an applied value of the secondtemperature increase amount ΔTi2 by multiplying the base value of thesecond temperature increase amount ΔTi2 by the first coefficient α1.

The temperature estimating module 52 obtains a decrease amount of theexhaust gas temperature due to (iv) the heat release to the upstreampart of the exhaust pipe (hereinafter, this decrease amount is referredto as the “second temperature decrease amount ΔTe2”). A traveling windblows around the engine body 20 and the exhaust system, and the enginebody 20 and the exhaust system are cooled by the traveling wind. Forexample, in the case where the turbocharger 4 is provided as it is inthe engine 100, the turbocharger 4 is structured so that the travelingwind is introduced to a circumference of the turbine housingaccommodating the turbine 4 b, and the upstream part of the exhaust pipeincluding the turbine housing is cooled well. Therefore, the heatrelease of the exhaust gas to the upstream part of the exhaust pipe whenthe exhaust gas passes therethrough increases. The internal memory ofthe ECU 50 stores in advance an upstream-side vehicle speed heat releasemap in which the second temperature decrease amount ΔTe2 based on thevehicle speed is defined. FIG. 10 is an image chart of the upstream-sidevehicle speed heat release map in which the second temperature decreaseamount ΔTe2 increases as the vehicle speed increases (i.e., the exhaustgas is cooled more). The temperature estimating module 52 obtains thesecond temperature decrease amount ΔTe2 by comparing the vehicle speedwith the upstream-side vehicle speed heat release map.

Note that although the heat release to the upstream part of the exhaustpipe also is influenced by the exhaust gas flow rate (intake air flowrate) and an outdoor air temperature, in this example, the vehicle speedcauses a dominant influence. Therefore, the second temperature decreaseamount ΔTe2 is determined based on the vehicle speed alone. However, thesecond temperature decrease amount ΔTe2 may be determined by taking intoconsideration one of the exhaust gas flow rate and the outdoor airtemperature.

The temperature estimating module 52 obtains a decrease amount of theexhaust gas temperature due to (v) the heat release to the downstreampart of the exhaust pipe (hereinafter, this decrease amount is referredto as the “third temperature decrease amount ΔTe3”). The exhaust gasreleases heat also to the part of the exhaust pipe downstream of theturbine 4 b, in addition to the upstream part of the exhaust pipedescribed above. With (iv) the heat release to the upstream part of theexhaust pipe, since the vehicle speed causes the dominant influencethereon, only the vehicle speed is taken into consideration, whereaswith (v) the heat release to the downstream part of the exhaust pipe,the influence from the vehicle speed is relatively small, and theexhaust gas flow rate (the intake air flow rate) and the outdoor airtemperature also have influence. The internal memory of the ECU 50stores in advance a downstream-side vehicle speed heat release map inwhich a base value of the third temperature decrease amount ΔTe3 basedon the vehicle speed is defined, a second coefficient map in which acoefficient based on the intake air flow rate (hereinafter, referred toas the “second coefficient α2”) is defined, and a third coefficient mapin which a coefficient based on the outdoor air temperature(hereinafter, referred to as the “third coefficient α3”) is defined.FIG. 11 is an image chart of the downstream-side vehicle speed heatrelease map in which the third temperature decrease amount ΔTe3increases as the vehicle speed increases (i.e., the exhaust gas iscooled more). FIG. 12 is an image chart of the second coefficient map inwhich the second coefficient α2 decreases as the intake air flow rateincreases (i.e., the exhaust gas is cooled less). FIG. 13 is an imagechart of the third coefficient map in which the third coefficient α3decreases as the outdoor air temperature increases (i.e., the exhaustgas is cooled less). The temperature estimating module 52 uses theintake air flow rate as a value relating to the exhaust gas flow rate.The temperature estimating module 52 uses the intake air temperaturedetected by the first temperature sensor 62 as the outdoor airtemperature. The temperature estimating module 52 obtains the base valueof the third temperature decrease amount ΔTe3 by comparing the vehiclespeed with the downstream-side vehicle speed heat release map, thesecond coefficient α2 by comparing the intake air flow rate with thesecond coefficient map, and the third coefficient α3 by comparing theoutdoor air temperature with the third coefficient map. The temperatureestimating module 52 obtains an applied value of the third temperaturedecrease amount ΔTe3 by multiplying the base value of the thirdtemperature decrease amount ΔTe3 by the second and third coefficients α2and α3.

The temperature estimating module 52 obtains a decrease amount of theexhaust gas temperature due to (vi) the heat loss caused by the work ofthe turbine, (hereinafter, this decrease amount is referred to as the“fourth temperature decrease amount ΔTe4”). When the exhaust gas rotatesthe turbine 4 b, the heat amount of the exhaust gas is converted intothe work of the turbine and the exhaust gas temperature decreases. Theamount of work acting on the turbine 4 b depends on the opening of theWG valve 36 and the turbine flow rate. The internal memory of the ECU 50stores in advance a work loss map in which a base value of the fourthtemperature decrease amount ΔTe4 based on the opening of the WG valve 36is defined, and a fourth coefficient map in which a coefficient based onthe turbine flow rate (hereinafter, referred to as the “fourthcoefficient α4”) is defined. FIG. 14 is an image chart of the work lossmap in which the fourth temperature decrease amount ΔTe4 decreases asthe opening of the WG valve 36 increases (i.e., the exhaust gas iscooled less). FIG. 15 is an image chart of the fourth coefficient map inwhich the fourth coefficient α4 increases as the turbine flow rateincreases (i.e., the exhaust gas is cooled more). The temperatureestimating module 52 obtains the base value of the fourth temperaturedecrease amount ΔTe4 by comparing the opening of the WG valve 36 withthe work loss map, and the fourth coefficient α4 by comparing theturbine flow rate with the fourth coefficient map. The temperatureestimating module 52 obtains an applied value of the fourth temperaturedecrease amount ΔTe4 by multiplying the base value of the fourthtemperature decrease amount ΔTe4 by the fourth coefficient α4.

The temperature estimating module 52 obtains an increase amount of theexhaust gas temperature due to (vii) the heating by the reaction heat ofthe exhaust emission control catalyst 37 (hereinafter, this increaseamount is referred to as the “third temperature increase amount ΔTi3”).The exhaust emission control catalyst 37 purifies the exhaust gas byreduction and/or oxidation, and produces the reaction heat during thepurification. Thus, the exhaust gas temperature increases. The amount ofreaction heat depends on amounts of NOR, CO and HC within the exhaustgas (corresponding to the engine speed and the charge efficiency), andpurifying performance of the exhaust emission control catalyst 37(corresponding to the air-fuel ratio). The internal memory of the ECU 50stores in advance a reaction heat map in which a base value of the thirdtemperature increase amount ΔTi3 based on the engine speed and thecharge efficiency is defined, and a fifth coefficient map in which acoefficient based on the air-fuel ratio (hereinafter, referred to as the“fifth coefficient α5”) is defined. FIG. 16 is an image chart of thereaction heat map in which the third temperature increase amount ΔTi3increases as one of the engine speed and the charge efficiency increases(i.e., the exhaust gas is heated more). FIG. 17 is an image chart of thefifth coefficient map in which the fifth coefficient α5 decreases (i.e.,the exhaust gas is heated less) as the air-fuel ratio shifts to bericher (the air-fuel ratio decreases) from the stoichiometric ratio(14.7:1). This is because the purification efficiency of the exhaustemission control catalyst 37 is high when the air-fuel ratio isstoichiometric, and decreases as the air-fuel ratio shifts to be richer.Note that in this example, even when the air-fuel ratio is lean, thefifth coefficient α5 does not change greatly. However, depending on theengine 100 and the exhaust emission control catalyst 37, the fifthcoefficient α5 may become smaller as the air-fuel ratio shifts to beleaner. The temperature estimating module 52 obtains the base value ofthe third temperature increase amount ΔTi3 by comparing the engine speedand the charge efficiency with the reaction heat map, and the fifthcoefficient α5 by comparing the air-fuel ratio with the fifthcoefficient map. The temperature estimating module 52 obtains an appliedvalue of the third temperature increase amount ΔTi3 by multiplying thebase value of the third temperature increase amount ΔTi3 by the fifthcoefficient α5.

The temperature estimating module 52 obtains an increase amount of theexhaust gas temperature due to (viii) the heat reception caused by theafterburn at the exhaust emission control catalyst 37 (hereinafter, thisincrease amount is referred to as the “fourth temperature increaseamount ΔTi4”). The afterburn during the blow-through of the fresh airoccurs not only at the manifold section 30 b described above, but alsoat the exhaust emission control catalyst 37. In other words, theunburned fuel within the exhaust gas does not completely burn in themanifold section 30 b and the exhaust pipe downstream thereof, and apart of the unburned fuel remains unburned and reaches the exhaustemission control catalyst 37. As described above, since the exhaustemission control catalyst 37 is increased in temperature by the reactionheat, the remaining unburned fuel easily combusts at the exhaustemission control catalyst 37. Thus, the afterburn also occurs at theexhaust emission control catalyst 37. The internal memory of the ECU 50stores in advance a second afterburn map in which the fourth temperatureincrease amount ΔTi4 based on the blow-through flow rate is defined.FIG. 18 is an image chart of the second afterburn map in which acharacteristic of the fourth temperature increase amount ΔTi4 inrelation to the blow-through flow rate is defined for every air-fuelratio. When the air-fuel ratio is fixed, the fourth temperature increaseamount ΔTi4 decreases as the blow-through flow rate increases (i.e., theexhaust gas is heated less). Further, when the blow-through flow rate isfixed, the fourth temperature increase amount ΔTi4 decreases (i.e., theexhaust gas is heated less) as the air-fuel ratio decreases (i.e., theair-fuel ratio becomes richer). This is because, when the air-fuel ratiois low, or in other words, when the fuel amount is relatively large, theafterburn is less likely to occur since the cooling effect caused by thelatent heat of the vaporization of the fuel increases. When the fuelamount becomes relatively small, the influence of the heating by theafterburn becomes larger than that of the cooling by the latent heat ofthe vaporization of the fuel. The temperature estimating module 52obtains the fourth temperature increase amount ΔTi4 by comparing theblow-through flow rate and the air-fuel ratio with the second afterburnmap.

The temperature estimating module 52 estimates the exhaust gastemperatures at the plurality of locations in the exhaust system, byadding to or subtracting from the discharging temperature T0, with anyof the first to fourth temperature increase amounts ΔTi1 to ΔTi4 and thefirst to fourth temperature decrease amounts ΔTe1 to ΔTe4 as needed. Forexample, the first exhaust gas temperature Ta is obtained by subtractingthe first temperature decrease amount ΔTe1 from the dischargingtemperature T0. The second exhaust gas temperature Tb is obtained bysubtracting the first temperature decrease amount ΔTe1 from thedischarging temperature T0, adding the first and second temperatureincrease amounts ΔTi1 and ΔTi2 thereon, and then subtracting therefromthe second temperature decrease amount ΔTe2. The third exhaust gastemperature Tc is obtained by subtracting the first temperature decreaseamount ΔTe1 from the discharging temperature T0, adding the first andsecond temperature increase amounts ΔTi1 and ΔTi2 thereto, andsubtracting therefrom the second to fourth temperature decrease amountsΔTe2 to ΔTe4. The fourth exhaust gas temperature Td is obtained bysubtracting the first temperature decrease amount ΔTe1 from thedischarging temperature T0, adding the first and second temperatureincrease amounts ΔTi1 and ΔTi2 thereon, then subtracting therefrom thesecond to fourth temperature decrease amounts ΔTe2 to ΔTe4, and addingthe third and fourth temperature increase amounts ΔTi3 and ΔTi4. Notethat the temperature estimating module 52, when calculating the first tofourth exhaust gas temperatures Ta to Td, performs the calculations bysuitably using a primary delay element, in consideration of heatcapacities of the respective components of the exhaust system. Any ofthe discharging temperature T0, the first to fourth temperature increaseamounts ΔTi1 to ΔTi4, and the first to fourth temperature decreaseamounts ΔTe1 to ΔTe4 may be the primary delay element as needed.

According to the temperature estimation by the temperature estimatingmodule 52 described above, even when the blow-through flow rate is high,the exhaust gas temperatures are estimated by taking into considerationthe temperature increase of the exhaust gas caused by the afterburns. Asa result, the exhaust gas temperatures are estimated accurately.

Fuel Amount Increase

Next, the fuel amount increase control by the increasing amountcontrolling module 53 and the overlapping period adjustment by the valvecontrolling module 54 in the control are described with reference toFIG. 19. FIG. 19 is a flowchart illustrating processing of the fuelamount increase control.

First at S201, the temperature estimating module 52 acquires theoperating state of the engine 100. Specifically, the engine speed, thecharge efficiency, the ignition timing, the air-fuel ratio, etc. areread based on the detection results of the various sensors.

Next at S202, the temperature estimating module 52 calculates thedischarging temperature T0, the first to fourth temperature increaseamounts ΔTi1 to ΔTi4, and the first to fourth temperature decreaseamounts ΔTe1 to ΔTe4 based on the operating state read at S201, andestimates the exhaust gas temperatures Ta to Td at the respectivelocations in the exhaust system.

Subsequently at S203, among the exhaust gas temperatures estimated bythe temperature estimating module 52, the increasing amount controllingmodule 53 reads the second exhaust gas temperature Tb at the positionimmediately upstream of the turbine 4 b. Further, the increasing amountcontrolling module 53 determines whether the fuel amount increasecontrol is required, based on the second exhaust gas temperature Tb.Specifically, when the second exhaust gas temperature Tb is above agiven amount-increase determination temperature, it is determined thatthe second exhaust gas temperature Tb is required to be decreased inorder to prevent an excessive temperature increase of the turbine 4 b,and the fuel amount increase is requested. The amount-increasedetermination temperature is defined based on a guaranteed operationtemperature of the turbine 4 b and stored in the internal memory of theECU 50 in advance. On the other hand, when the second exhaust gastemperature Tb is the amount-increase determination temperature orbelow, it is determined that the second exhaust gas temperature Tb isnot required to be decreased, and the fuel amount increase is notrequested, and the control flow returns. Note that the configuration inwhich whether the fuel amount increase control is required is determinedbased on the comparison result between the second exhaust gastemperature Tb and the guaranteed operation temperature of the turbine 4b is merely an example, and it is not limited to this. For example, thedetermination may be performed by comparing the first exhaust gastemperature Ta (the exhaust gas temperature at the exit of the exhaustport 31) with an amount-increase determination temperature defined basedon a guaranteed operation temperature of the exhaust port 31, performedby comparing the third exhaust gas temperature Tc (the exhaust gastemperature at the O₂ sensor 67) with an amount-increase determinationtemperature defined based on a guaranteed operation temperature of theO₂ sensor 67, performed by comparing the fourth exhaust gas temperatureTd (the exhaust gas temperature at the exhaust emission control catalyst37) with an amount-increase determination temperature defined based on aguaranteed operation temperature of the exhaust emission controlcatalyst 37, or performed based on a combination of the comparisonresults from the respective locations in the exhaust system.

Next, at S204 which follows if the fuel amount increase is requested atS203, the increasing amount controlling module 53 obtains an increaseamount of the fuel in the fuel amount increase control (hereinafter,referred to as the “injection amount correction value”). The internalmemory of the ECU 50 stores in advance an amount increase map in whichthe injection amount correction value based on the engine speed and thecharge efficiency is defined. In the amount increase map, the injectionamount correction value increases as the engine speed increases and thecharge efficiency increases (i.e., the fuel amount is increased more).The increasing amount controlling module 53 obtains the injection amountcorrection value by comparing the engine speed and the charge efficiencywith the amount increase map. The increasing amount controlling module53 acquires a target value of the injection amount in the fuel amountincrease control (hereinafter, referred to as the“amount-increase-controlled injection amount”) by adding the injectionamount correction value to the base value of the injection amount set bythe base setting module 51.

Then at S205, the temperature estimating module 52 estimates the exhaustgas temperatures in the case where the fuel amount increase control isperformed, before the fuel amount increase control is actuallyperformed. Specifically, the temperature estimating module 52 obtainsthe first to fourth exhaust gas temperatures Ta to Td when the fuelamount increase control is performed. Hereinafter, the first to fourthexhaust gas temperatures Ta to Td for the case where the fuel amountincrease control is performed are referred to as the first to fourthestimated exhaust gas temperatures Ta′ to Td′. The temperatureestimating module 52 calculates the first to fourth estimated exhaustgas temperatures Ta′ to Td′ by obtaining the discharging temperature T0,the first to fourth temperature increase amounts ΔTi1 to ΔTi4, and thefirst to fourth temperature decrease amounts ΔTe1 to ΔTe4 again, for thecase where the fuel amount increase control is performed. Hereinafter,the discharging temperature T0, the first to fourth temperature increaseamounts ΔTi1 to ΔTi4, and the first to fourth temperature decreaseamounts ΔTe1 to ΔTe4 in the case where the fuel amount increase controlis performed are referred to as the discharging temperature T0′, thefirst to fourth temperature increase amounts ΔTi1′ to ΔTi4′, and thefirst to fourth temperature decrease amounts ΔTe1′ to ΔTe4 ′,respectively. In this embodiment, the discharging temperature T0′ andthe second to fourth temperature increase amounts ΔTi2′ to ΔTi4′ may beinfluenced by the fuel amount increase control as described below. Therest of the changing amounts of temperature remain the same as thosecalculated at S202.

The temperature estimating module 52 obtains the discharging temperatureT0′ by taking into consideration an influence of cooling of the exhaustgas by the fuel amount increase control. As described above, thetemperature inside the cylinder 21 is decreased by the latent heat ofthe vaporization of the amount-increased fuel. By the increase of thefuel amount, since the air-fuel ratio shifts to the rich side, thedischarging temperature T0′ obtained by the temperature estimatingmodule 52 based on the exhaust gas temperature map described abovebecomes lower than the discharging temperature TO obtained at S202. Thedecrease amount of the discharging temperature T0′ by the fuel amountincrease control becomes larger as the injection amount correction valueincreases (i.e., the exhaust gas discharged from the cylinder 21 iscooled more as the fuel amount increases). The temperature estimatingmodule 52 obtains the discharging temperature T0′ in the above-describedmanner, by using an amount-increase-controlled air-fuel ratio.

Further, the temperature estimating module 52 obtains the second andfourth temperature increase amounts ΔTi2′ and ΔTi4′ by taking intoconsideration an influence of the fuel amount increase control on theafterburns. The amount-increased fuel is supplied to the exhaust systemas the unburned fuel, which may cause the afterburns in the exhaust pipeand the exhaust emission control catalyst 37 as described above.Therefore, when the fuel amount increase control is performed, theafterburns easily occur according to the increased amount, and thesecond and fourth temperature increase amounts ΔTi2′ and ΔTi4 ′ maybecome higher than the second and fourth temperature increase amountsΔTi2 and ΔTi4 obtained at S202, respectively. The temperature estimatingmodule 52 obtains the second and fourth temperature increase amountsΔTi2′ and ΔTi4′ in the above-described manner, by using theamount-increase-controlled air-fuel ratio.

Moreover, the temperature estimating module 52 obtains the thirdtemperature increase amount ΔTi3′ by taking into consideration theinfluence of the fuel amount increase control on the reaction heat ofthe exhaust emission control catalyst 37. When the air-fuel ratio isdecreased by the fuel amount increase control, the purifying performanceof the exhaust emission control catalyst 37 drops, and the reaction heatdecreases. As a result, the third temperature increase amount ΔTi3′becomes lower than the third temperature increase amount ΔTi3 obtainedat S202. The temperature estimating module 52 obtains the thirdtemperature increase amount ΔTi3′ in the above-described manner, byusing the amount-increase-controlled air-fuel ratio.

Furthermore, the temperature estimating module 52 calculates the firstto fourth estimated exhaust gas temperatures Ta′ to Td′ based on thedischarging temperature T0′, the first to fourth temperature increaseamounts ΔTi1′ to ΔTi4′, and the first to fourth temperature decreaseamounts ΔTe1′ to ΔTe4′. For example, the first estimated exhaust gastemperature Ta′ is obtained by subtracting the first temperaturedecrease amount ΔTe1′ from the discharging temperature T0′, similar tothe calculation of the first exhaust gas temperature Ta. The secondestimated exhaust gas temperature Tb′ is obtained by adding the firstand second temperature increase amounts ΔTi1′ and ΔTi2′ to the firstestimated exhaust gas temperature Ta′ and subtracting the secondtemperature decrease amount ΔTe2′ therefrom. The third estimated exhaustgas temperature Tc′ is obtained by subtracting the third and fourthtemperature decrease amounts ΔTe3′ and ΔTe4′ from the second estimatedexhaust gas temperature Tb′. The fourth estimated exhaust gastemperature Td′ is obtained by adding the third and fourth temperatureincrease amounts ΔTi3′ and ΔTi4′ to the third estimated exhaust gastemperature Tc′. In the calculations of the first to fourth estimatedexhaust gas temperatures Ta′ to Td′, similar to the first to fourthestimated exhaust gas temperatures Ta to Td, a primary delay is suitablytaken into consideration.

Next, in the case where the increasing amount controlling module 53performs the fuel amount increase control, at S206, the valvecontrolling module 54 determines whether a protection for components ofthe exhaust system (in this embodiment, the exhaust ports 31, theturbine 4 b, the O₂ sensor 67, and the exhaust emission control catalyst37) is required, based on the temperature increase of the exhaust gas inthe fuel amount increase control. Specifically, in this embodiment,before the fuel amount increase is actually started, the valvecontrolling module 54 determines whether the fourth estimated exhaustgas temperature Td′ at the exhaust emission control catalyst 37 is abovea given protection determination temperature corresponding to theexhaust emission control catalyst 37. In this embodiment, the protectiondetermination temperature is defined based on the guaranteed operationtemperature of the exhaust emission control catalyst 37 (i.e., in thecase where the fuel amount increase control is performed, whether thetemperature of the exhaust emission control catalyst 37 exceeds theguaranteed operation temperature is determined). Further, if the fourthestimated exhaust gas temperature Td′ is determined to be above theprotection determination temperature, the valve controlling module 54determines that the protection for the components of the exhaust systemis required (proceeds to S207). On the other hand, if the fourthestimated exhaust gas temperature Td′ is determined to be the same as orbelow the protection determination temperature, the protection for thecomponents of the exhaust system is determined to not be required andthe increasing amount controlling module 53 starts increasing theinjection amount (proceeds to S209). Note that, in this embodiment, whenthe fourth estimated exhaust gas temperature Td′ at the exhaust emissioncontrol catalyst 37 is below the protection determination temperature,the first estimated exhaust gas temperature Ta′ at the exhaust port 31,the second estimated exhaust gas temperature Tb′ at the turbine 4 b, andthe third estimated exhaust gas temperature Tc′ at the O₂ sensor 67 donot exceed the guaranteed operation temperatures of the correspondingcomponents of the exhaust system. Alternatively, whether the protectionfor the components of the exhaust system is required may be determinedbased on one of the first estimated exhaust gas temperature Ta′ at theexhaust port 31, the second estimated exhaust gas temperature Tb′ at theturbine 4 b, and the third estimated exhaust gas temperature Tc′ at theO₂ sensor 67, or based on a combination of at least two of the first tofourth estimated exhaust gas temperatures Ta′ to Td′, instead of beingbased on the fourth estimated exhaust gas temperature Td′ at the exhaustemission control catalyst 37.

Subsequently at S207, the valve controlling module 54 obtains ashortening amount of the overlapping period (hereinafter, referred to asthe “overlap reduction amount”). By shortening the overlapping period,the components of the exhaust system can be protected. The overlapreduction amount is obtained based on the estimated exhaust gastemperatures Ta′ to Td′ for the case where the fuel amount increasecontrol is performed. In this embodiment, the overlap reduction amountis obtained based on the fourth estimated exhaust gas temperature Td′ atthe exhaust emission control catalyst 37 which is used for thedetermination described above. Specifically, as described above, thefourth estimated exhaust gas temperature Td′ is obtained based on thedischarging temperature T0′, the first to fourth temperature increaseamounts ΔTi1′ to ΔTi4′, and the first to fourth temperature decreaseamounts ΔTe1′ to ΔTe4′ which are obtained by taking into considerationthe influence of the fuel amount increase control. Among thesetemperature and temperature amounts, the first temperature decreaseamount ΔTe1′ and the second and fourth temperature increase amountsΔTi2′ and ΔTi4′ may be influenced by the blow-through flow rate of thefresh air. A blow-through flow rate required for decreasing the fourthestimated exhaust gas temperature Td′ down to a fourth guaranteedoperation temperature Ta4 or below is obtained by inverse calculationsof the first temperature decrease amount ΔTe 1′ and the second andfourth temperature increase amounts ΔTi2′ and ΔTi4′. Since theblow-through flow rate is obtained by multiplying the blow-through ratecorresponding to the overlapping amount by the intake air flow rate asdescribed above, by the inverse calculations thereof, the overlappingamount corresponding to the blow-through flow rate (i.e., the overlapreduction amount) required for decreasing the fourth estimated exhaustgas temperature Td′ down to the fourth guaranteed operation temperatureTa4 or below is obtained. In this manner, the valve controlling module54 obtains the blow-through flow rate required for decreasing the fourthestimated exhaust gas temperature Td′ down to the fourth guaranteedoperation temperature Ta4 or below, and acquires the overlap reductionamount corresponding to the blow-through flow rate. Further, the overlapreduction amount increases as the fourth estimated exhaust gastemperature Td′ increases above the fourth guaranteed operationtemperature Tt4. Note that the overlap reduction amount may be obtainedbased on one of the first to third estimated exhaust gas temperaturesTa′ to Tc′, or based on a combination of at least two of the first tofourth estimated exhaust gas temperatures Ta′ to Td′, without limitingto the fourth estimated exhaust gas temperature Td′.

At S208, the valve controlling module 54 activates the exhaust VVT 26 toadvance the close timing of the exhaust valve 29 by the overlapreduction amount obtained at S207. In this manner, the overlappingperiod in which the intake and exhaust valves 22 and 29 are both openedon the intake stroke is shortened. The valve controlling module 54shortens the overlapping period and then the increasing amountcontrolling module 53 starts the fuel amount increase.

Next at S209, the increasing amount controlling module 53 performs thefuel amount increase control (starts increasing the fuel amount).Specifically, the increasing amount controlling module 53 increases theinjection amount set by the base setting module 51, to theamount-increase-controlled injection amount acquired at S204 describedabove.

By performing the fuel amount increase control, the dischargingtemperature T0 decreases according to the latent heat of thevaporization, and the exhaust gas temperatures at the respectivelocations in the exhaust system, for example, the first exhaust gastemperature Ta at the exhaust port 31, is decreased. On the other hand,by performing the fuel amount increase control, the temperatures at therespective components of the exhaust system may exceed the guaranteedoperation temperatures thereof due to the temperature increase of theexhaust gas caused by the afterburns. As described at S206 to S209above, if there is a possibility of such a problem occurring, thecomponents of the exhaust system are protected by shortening theoverlapping period. Specifically, by shortening the overlapping period,the blow-through flow rate of the fresh air decreases. When theblow-through flow rate decreases, although the first temperaturedecrease amount ΔTe1 decreases and the temperature of the exhaust port31 increases, the temperature increase of the exhaust gas caused by theafterburns is suppressed; in other words, the second and fourthtemperature increase amounts ΔTi2 and ΔTi4 are reduced by a reducedamount of oxygen supplied to the exhaust system. In the case where theoverlapping amount is reduced, a total of the decrease amounts of theexhaust gas temperature caused by the suppression of the afterburns islarger than the increase amount of the exhaust gas temperature caused bythe temperature increase of the exhaust port 31. Therefore, by reducingthe overlapping amount, the temperature increase of the exhaust gas issuppressed, which results in protecting the components of the exhaustsystem.

As described above, the ECU 50 includes the increasing amountcontrolling module 53 for performing the fuel amount increase control inwhich the injection amount of the fuel is increased so as to decreasethe exhaust gas temperature, and the valve controlling module 54 forcontrolling, via the intake and exhaust VVTs 25 and 26, the overlappingperiod in which the intake and exhaust valves 22 and 29 are both openedon the intake stroke of the engine 100. In the case where the increasingamount controlling module 53 performs the fuel amount increase control,the valve controlling module 54 determines whether the protection forthe components of the exhaust system (specifically, the exhaust ports31, the turbine 4 b, the O₂ sensor 67, and the exhaust emission controlcatalyst 37) is required, based on the second to fourth temperatureincrease amounts ΔTi2′ to ΔTi4 ′ indicating the temperature increase ofthe exhaust gas in the case where the fuel amount increase control isperformed. If the protection for the components of the exhaust system isdetermined to be required, the overlapping period is shortened.

According to this configuration, whether the protection for thecomponents of the exhaust system is required is determined based on theestimated temperature increase of the exhaust gas in the case where thefuel amount increase control is performed. Since the exhaust gastemperature increases when the afterburns occur, by performing thedetermination based on the estimated temperature increase of the exhaustgas, the timing at which the protection for the components of theexhaust system is required is determined more suitably. Further,according to this configuration, the overlapping period is shortenedwhen the protection for the components of the exhaust system isdetermined to be required. In this case, since the blow-through flowrate of the fresh air is decreased corresponding to the shortened amountof the overlapping period, the afterburns are suppressed according tothe decrease amount. Therefore, the temperature increase of thecomponents of the exhaust system is suppressed to protect thecomponents.

Further, if the valve controlling module 54 determines that theprotection for the components of the exhaust system is required, itshortens the overlapping period before the increasing amount controllingmodule 53 starts increasing the injection amount.

Generally, even if the overlapping period is shortened after the fuelamount increase control, the increased amount of fuel is supplied to theexhaust system before the blow-through flow rate of the fresh airdecreases. For this reason, the temperature increase of the exhaust gascaused by the afterburns may not be suppressed sufficiently.

According to the above configuration, the overlapping period isshortened before the fuel amount increase starts. Thus, by the time theincreased amount of fuel is supplied to the exhaust system, theblow-through flow rate of the fresh air has decreased already.Therefore, the afterburns are suppressed more surely, whichadvantageously results in protecting the components of the exhaustsystem.

Further, the valve controlling module 54 determines whether theprotection for the components of the exhaust system is required, basedon the flow rate of the fresh air blowing through to the exhaust systemin the overlapping period, and the fuel injection amount.

The exhaust gas temperature may increase due to the afterburns whichoccur as a result of the reaction of the fresh air blown through to theexhaust system with the unburned fuel, and the amount of the unburnedfuel changes according to the fuel injection amount. Thus, according tothe configuration above, by performing the determination inconsideration of the blow-through flow rate of the fresh air and thefuel injection amount, the temperature increase of the exhaust gascaused by the afterburns is accurately taken into consideration. Thus,whether the protection for the components of the exhaust system isrequired is accurately determined.

Moreover, when the estimated exhaust gas temperature in the case wherethe fuel amount increase control is performed is above the givenprotection determination temperature, the valve controlling module 54determines that the protection for the components of the exhaust systemis required.

Generally, the exhaust gas temperature is considered to increaseaccording to the estimated temperature increase of the exhaust gas.Thus, according to this configuration, by performing the determinationbased on the exhaust gas temperature, the timing at which the protectionfor the components of the exhaust system is required is determined moresuitably.

Further, the valve controlling module 54 sets the shortening amount ofthe overlapping period based on the temperature increase of the exhaustgas.

According to this configuration, by taking into consideration thetemperature increase of the exhaust gas in setting the shortening amountof the overlapping period, the temperature increase of the components ofthe exhaust system is suppressed more surely. For example, by increasingthe shortening amount as the estimated temperature increase of theexhaust gas becomes larger, the blow-through flow rate is decreased moreas the temperature increase becomes larger. Thus, the afterburns aresuppressed more sufficiently, and as a result, the temperature increaseof the components of the exhaust system is suppressed more surely.

Further, the valve controlling module 54, when shortening theoverlapping period, changes the close timing of the exhaust valve 29.

According to this configuration, compared with the case of changing theopen and close timings of the intake valve 22, an influence on theamount of the intake air supplied into the cylinder 21 is reduced and,as a result, by providing the overlapping period, the influence on theoutput torque of the engine 100 is advantageously reduced.

Moreover, the components of the exhaust system include the exhaustemission control catalyst 37.

According to this configuration, at least the exhaust emission controlcatalyst 37 is protected from the exhaust gas heat.

Other Embodiments

As above, the embodiment is described as an illustrative example of theart disclosed in the present application. However, the art of thisdisclosure is not limited to this, and also applicable to embodimentswith suitable modification(s), change(s), replacement(s), addition(s),omission(s), etc. Further, some of the components described in theembodiment may be combined to constitute a new embodiment. Moreover, thecomponents illustrated in the appended drawings and described in thedetailed description of the embodiments may include not only essentialcomponents for solving the above problems which occur with theconventional arts, but also non-essential components for solving theabove problems, in order to illustratively describe the art. Therefore,the non-essential components should not be considered as essentialsimply because they are illustrated in the appended drawings ordescribed in the detailed description of the embodiments.

The above embodiment may have any of the following configurations.

The configuration of the engine 100 described above is an example and isnot limited to this.

Further, the temperature estimating module 52 described above estimatesthe exhaust gas temperatures at the exit of the exhaust port 31, theposition immediately upstream of the turbine 4 b, the O₂ sensor 67, andthe exhaust emission control catalyst 37; however, it is not limited tothis. By taking into consideration the gain and loss of heat on theupstream side of the locations where the exhaust gas temperatures areestimated, the temperature estimating module 52 may estimate the exhaustgas temperature at any location in the exhaust system.

Further, for the gain and loss of heat, the temperature estimatingmodule 52 described above takes into consideration the first to fourthtemperature increase amounts ΔTi1 to ΔTi4 and the first to fourthtemperature decrease amounts ΔTe1 to ΔTe4; however, it is not limited tothis. Depending on the engine, there may exist a factor which has asmall influence on the exhaust gas temperature. In such a case,unnecessary one(s) of the first to fourth temperature increase amountsΔTi1 to ΔTi4 and the first to fourth temperature decrease amounts ΔTe1to ΔTe4 may be omitted. Alternatively, depending on the engine, theremay exist a different factor which has a large influence on the exhaustgas temperature. In such a case, the exhaust gas temperature may beestimated by further taking into consideration the different factor.

Further, for the influence of the afterburns, the temperature estimatingmodule 52 described above takes into consideration (iii) the heatreception caused by the afterburn at the position of the exhaust pipeupstream of the turbine 4 b and (viii) the heat reception caused by theafterburn at the exhaust emission control catalyst 37; however, it isnot limited to this. The temperature estimating module 52 may take intoconsideration only one of the afterburns or afterburn(s) at otherlocation(s).

Further, the various maps used by the temperature estimating module 52are merely an example, and characteristics of the various maps varydepending on the engine.

Further, the valve controlling module 54 determines that the protectionfor the components of the exhaust system is required, when the fourthestimated exhaust gas temperature Td′ at the exhaust emission controlcatalyst 37 is above the protection determination temperaturecorresponding to the exhaust emission control catalyst 37; however, itis not limited to this. The valve controlling module 54 may determinethat the protection for the components of the exhaust system isrequired, when the temperature of the exhaust emission control catalyst37 is above a given determination component temperature. Thedetermination component temperature is defined based on the guaranteedoperation temperature of the exhaust emission control catalyst 37.Similarly, the determination may be performed based on the temperatureof the exhaust port 31, the temperature of the turbine 4 b, thetemperature of the O₂ sensor 67, or a combination of at least two of thetemperatures of the exhaust port 31, the turbine 4 b, the O₂ sensor 67,and the exhaust emission control catalyst 37. Moreover, the shorteningamount of the overlapping period may be set based on the temperatures ofthe respective components of the exhaust system.

Further, the valve controlling module 54 shortens the overlapping periodby advancing the close timing of the exhaust valve 29; however, it isnot limited to this. The valve controlling module 54 may shorten theoverlapping period by retarding the open timing of the intake valve 22,or by advancing the close timing of the exhaust valve 29 and alsoretarding the open timing of the intake valve 22.

Further, by shortening the overlapping period, the valve controllingmodule 54 protects the exhaust port 31, the turbine 4 b, the O₂ sensor67, and the exhaust emission control catalyst 37 as the components ofthe exhaust system; however, it is not limited to this. The valvecontrolling module 54 may protect any component of the exhaust system byperforming the determination based on the temperature increase of theexhaust gas.

As described above, the art disclosed here is useful for the controlapparatus of the engine.

It should be understood that the embodiments herein are illustrative andnot restrictive, since the scope of the invention is defined by theappended claims rather than by the description preceding them, and allchanges that fall within metes and bounds of the claims, or equivalenceof such metes and bounds thereof, are therefore intended to be embracedby the claims.

LIST OF REFERENCE CHARACTERS

100 Engine

20 Engine Body

21 Cylinder

22 Intake Valve

25 Intake VVT

26 Exhaust VVT

29 Exhaust Valve

30 Exhaust Passage

30 a Branched Pipe

30 b Manifold Section

31 Exhaust Port

37 Exhaust Emission Control Catalyst (Catalyst)

4 Turbocharger

4 b Turbine

50 ECU (Control Apparatus)

52 Temperature Estimating Module

53 Increasing Amount Controlling Module

54 Valve Controlling Module

What is claimed is:
 1. A control apparatus of an engine including anintake valve, an exhaust valve, and a variable valve timing mechanismfor varying open and close timings of at least one of the intake andexhaust valves, the control apparatus comprising a processor configuredto execute: an increasing amount controlling module for performing afuel amount increase control in which an injection amount of fuel isincreased so as to decrease a temperature of exhaust gas; and a valvecontrolling module for controlling, via the variable valve timingmechanism, an overlapping period in which the intake and exhaust valvesare both opened on intake stroke of the engine, wherein when theincreasing amount controlling module performs the fuel amount increasecontrol, based on a temperature increase of the exhaust gas estimated tooccur due to the fuel amount increase control, the valve controllingmodule determines whether a protection for a component of an exhaustsystem of the engine is required, and if the protection for thecomponent of the exhaust system is determined to be required, the valvecontrolling module shortens the overlapping period.
 2. The controlapparatus of claim 1, wherein if the protection for the component of theexhaust system is determined to be required, the valve controllingmodule shortens the overlapping period before the increasing amountcontrolling module starts increasing the injection amount.
 3. Thecontrol apparatus of claim 1, wherein the valve controlling moduledetermines whether the protection for the component of the exhaustsystem is required, based on a flow rate of fresh air blowing through tothe exhaust system in the overlapping period, and the injection amount.4. The control apparatus of claim 1, wherein the valve controllingmodule determines that the protection for the component of the exhaustsystem is required, in the case where the fuel amount increase controlis performed and the exhaust gas temperature is above a given protectiondetermination temperature, or in the case where the fuel amount increasecontrol is performed and a temperature of the component of the exhaustsystem is above a given determination component temperature.
 5. Thecontrol apparatus of claim 1, wherein the valve controlling module setsa shortening amount of the overlapping period based on the temperatureincrease of the exhaust gas.
 6. The control apparatus of claim 1,wherein the valve controlling module changes the open and close timingsof the exhaust valve when shortening the overlapping period.
 7. Thecontrol apparatus of claim 1, wherein the component of the exhaustsystem at least includes a catalyst for purifying the exhaust gas.
 8. Acontrol apparatus of an engine including an intake valve, an exhaustvalve, and a variable valve timing mechanism for varying open and closetimings of at least one of the intake and exhaust valves, the controlapparatus comprising a processor configured to execute: an increasingamount controlling module for setting an injection amount of fuel inresponse to a request from a driver and performing, based on atemperature of exhaust gas, a fuel amount increase control in which theinjection amount of the fuel is increased so as to decrease thetemperature of the exhaust gas; and a valve controlling module forcontrolling, via the variable valve timing mechanism, an overlappingperiod in which the intake and exhaust valves are both opened on intakestroke of the engine, wherein when the increasing amount controllingmodule performs the fuel amount increase control, based on a temperatureincrease of the exhaust gas estimated to occur due to the fuel amountincrease control, the valve controlling module determines whether aprotection for a component of an exhaust system of the engine isrequired, and if the protection for the component of the exhaust systemis determined to be required, the valve controlling module shortens theoverlapping period.